- Why has fence integration with a segmental retaining wall become such hot topic in recent years?
- What are the specific code requirements of concern when integrating a fence with a segmental retaining wall?
- How has fence integration been addressed in the past?
- Why is the buffer zone concept problematic?
- Can I install the fence in the wall face or directly behind it?
- How is the Sleeve-It™ System any different then using a sonotube?
- How is the cost of using the Sleeve-It™ System justified?
- Are there any concerns with the fence foundation’s depth when using the Sleeve-It™ System?
- Is there more then one size for the Sleeve-It™ System and what is the appropriate nomenclature?
Q: Why has fence integration with a segmental retaining wall become such hot topic in recent years?
A: The International Building Code (IBC) of 2003 has recently been adopted at various levels by 48 states. This code clearly defines that a fence is required where a fall hazard is present. As the code becomes more readily enforced it is easily realized that the construction of a retaining wall creates the very fall hazard that triggers the enforcement of this code. With the primary focus being on wall design and construction it is often not realized that a fence has its own design requirements and to integrate it with the wall those requirements are not achievable with out additional design considerations.
Q: What are the specific code requirements of concern when integrating a fence with a segmental retaining wall?
A: The IBC section 1607.7.1 addresses requirements for fencing. When a retaining wall reaches heights in the 18” – 48” range (local municipal dependent), a fall hazard is created that triggers the code requiring a fence. The fence system must also be able to resist concentrated loads ranging from 200lb to 500lbs.
Q: How has fence integration been addressed in the past?
A: Most of the technical information available requires fencing be installed a minimum three feet away from the wall face. The creation of this “Buffer Zone” between the fence post foundation and wall face in theory allows any load applied to the fence system to be absorbed by the passive resistance of the soil before it affects the integrity of the wall face. It has also been widely accepted that a forming tube should be placed during wall construction so fence posts can be installed without running a power auger through the walls reinforced soil and top geogrid layers.
Q: Why is the buffer zone concept problematic?
A: With the primary function of an SRW being to maximize useable real estate it is often not realized that land use will not be available to the segmental wall face. Work stoppages have become common place caused by last minute redesigns and lengthy municipal review periods. Maintenance and safety issues related to having three feet of “dead space” on the hazard side of the fence are also prevailing concerns. During wall installation there is often a loss of production and poor compaction practices within this fence integration zone.
Q: Can I install the fence in the wall face or directly behind it?
A: There is some technical information available that show fence posts integrated in the wall face of an SRW or directly behind it. This information typically have disclaimers stating: “Design by Others”, “Not for Construction”, or “Per fence manufacturer specifications.” These details often show up on construction plans and bid documents without anyone assuming responsibility for the design. When the wall goes in for final engineering, the wall designer will almost always use the “buffer zone” concept to satisfy the liability concern related to placing the fence closer to the wall face. This is where the miscommunication can begin because the change in details from original bid documents to final construction drawings often goes unnoticed until the wall is under construction or even completed.
Q: How is the Sleeve-It™ System any different then using a sonotube?
A: A sonotube® is made of a cardboard type material and is used as a form that is filled with concrete for a variety of construction related activities. In the manufacturer’s written specification and stamped clearly on the side of each tube it states that it will not be able to handle vibration or moisture prior to the concrete pour. Two key ingredients related to backfilling a segmental retaining wall are obtaining compaction through vibration with the soil having a defined moisture ratio. The Sleeve-It™ System’s corrugated HDPE cylinder is designed to handle the weight of backfill soils and vibratory compactors as well as durable enough to handle moisture related conditions and long periods of inactivity between the end of wall construction and the actual fence installation. The system’s lid component prevents collection of debris during and after the wall installation. The real focus however is on the pre-engineered steel components that allow the system to be installed directly behind the wall face in a code compliant manner.
Q: How is the cost of using the Sleeve-It™ System justified?
A: The Sleeve-It™ System’s cost can be directly related to the value of gained real estate in a code compliant manner and the elimination of long term maintenance and safety concerns. Because it is a fence post foundation system the cost can be equally spread between wall construction and the fence installation. Fence installation requires layout, augering holes, placing posts, and installing the fence. The wall installer is essentially doing half the job for the fence installer during wall construction. The only coordination necessary is for the fence installer to provide proper spacing requirements.
Q: Are there any concerns with the fence foundation’s depth when using the Sleeve-It™ System?
A: Fence foundations are often in excess of 36” deep for two reasons: resistance to overturning and for freeze thaw protection. The Sleeve-It™ units are 24”-32” deep dependant on the application. The engineered steel components provide a cantilever footing to prevent overturning on the wall face side and the passive resistance of soil compacted to 95% on the backside. The system is also placed in the ¾”clean stone fill behind the wall decreasing the likelihood of movement in a freeze thaw cycle. A segmental retaining wall is dry-stacked and designed to have some movement in the freeze thaw cycles. With the fence foundation system being an accessory component to a flexible wall system freeze thaw is not a concern.
Q: Is there more then one size for the Sleeve-It™ System and what is the appropriate nomenclature?
A: Yes, when using the Sleeve-It™ System it should be understood that it is a product line. The Sleeve-It™ 1224R is currently available for typical commercial/residential applications where a 500lb concentrated load or 50plf requirement is the case. The Sleeve-It™ 0824R is currently under development to satisfy the 200lb concentrated load requirement. Until then the 1224R works well for both requirements. The Sleeve-It™ 1632R is also under development as a guide rail foundation system. This unit is being designed for the IBC requirement of a 6000lb concentrated load at 18” off grade. All three sizes are collectively referred to as the Sleeve-It™ System . When referring to a specific application the numbering system defines the appropriate unit. For example the Sleeve-It™ 1224R is ideal for chain link fences up to 8’0”. The numbering system defines the diameter and depth of the sleeve component with the “R” referring to the steel Reinforcement.
